Using LDAP keyservers with gpg 2.1

[Philip Colmer]

I've configured our LDAP server to act as a keyserver for use with
GnuPG. In testing, with version 1.x and 2.0, sending keys to the
keyserver works.

However, with version 2.1.11, it isn't working. Part of the challenge
seems to be how to specify authentication information in gpg 2.1 but
I've also tried temporarily changing the permissions on our LDAP
server so that anyone can write to the appropriate OU and it still
fails:

gpg: sending key DC6F3C29 to ldaps://login.linaro.org
gpg: DBG: chan_3 -> KS_PUT
gpg: DBG: chan_3 <- INQUIRE KEYBLOCK
gpg: DBG: chan_3 -> [ 44 20 99 01 25 30 44 04 56 fe 8f d2 01 08 00 c2
...(982 byte(s) skipped) ]
gpg: DBG: chan_3 -> [ 44 20 20 4f ad 28 53 1c 95 8a ae 0f 57 5f 35 fc
...(231 byte(s) skipped) ]
gpg: DBG: chan_3 -> END
gpg: DBG: chan_3 <- INQUIRE KEYBLOCK_INFO
gpg: DBG: chan_3 -> D
pub:e:2048:1:4625A9B1DC6F3C29:1459523538:1460128338::::::::::%0Auid:::::1459523538::::Philip
Colmer <philip.colmer at linaro.org>:::::::%0Asig::::4625A9B1DC6F3C29:1459523538:::::::::::%0Asub:e:2048:1:87E613C66F047E92:1459523538:1460128338::::::::::%0A
gpg: DBG: chan_3 -> END
gpg: DBG: chan_3 <- ERR 767 Cannot contact LDAP server <Unspecified source>

This is with the gpg configuration set to guru debug level.

How can I debug this further, please? I suspect that the actual error
is getting buried somewhere, unfortunately.

Regards

Philip